1. Field of the Invention
The present invention relates to a probe apparatus and, more particularly, it relates to a probe apparatus for examining electric characteristics of objects such as semiconductor wafers while contacting probes of the probe apparatus with electrode pads of each of the wafers.
2. Description of the Related Art
The probe apparatus has been well-known as a means for examining electric characteristics of objects such as semiconductor wafers.
One of the conventional probe apparatuses of this type has such an arrangement as shown in FIG. 1. More specifically, it comprises a table 11 attached to an apparatus body 1, which can be moved in horizontal and vertical directions, and on which a wafer 10 is mounted, a probe card 13 arranged above the wafer-mounted table 11 and provided with probes 12 which are contacted with electrode pads of the wafer 10, and a test head 15 contacted with contact elements 18 on the top of the probe card 13 through input/output pins 14 to convert electric signals applied from the probe card 13. The test head 15 is connected to a measuring equipment located outside through a plurality of wirings in a cable 16. Hinges 17 are attached to the test head 15 to enable the latter to be swung in those directions which are shown by arrows in FIG. 1. A manipulator (not shown) is attached to one side of the apparatus body 1 to move up and down the probe card 13 and the test head 15 as a unit.
When electric characteristics of the wafer 10 are to be examined by the above-arranged probe apparatus, the test head 15 is moved and set relative to the top of the probe card 13. Electrode pads of the wafer 10 on the wafer-mounted table 11 are aligned with probes of the probe card 13 by an alignment device (not shown). The probe card 13 is moved downward together with the test head 15 to contact the probes 12 of the probe card 13 with the electrode pads of the wafer 10. Electric characteristics of the wafer 10 are thus examined.
In the case of this probe apparatus, however, the number of input/output pins must be increased and the wiring must be made more complicated as the number of electrodes of the wafer is increased. This makes the test head 15 extremely heavy or 800 kg, for example. In addition, the diameter of the cable 16 through which the test head 15 is connected to the external measuring equipment must be made larger. The structure of the apparatus body 1 must also be made more rigid to make stronger the hinge system by which the test head 15 is swung. Therefore, the probe apparatus becomes larger-sized. Further, there is a fear that wirings in the cable are broken because the diameter of the cable becomes larger and because a more excessive load is thus added to the cable when the test head 15 is to be swung.
In the case of the above-arranged probe apparatus, too, it cannot be avoided that the cable through which the test head 15 is connected to the external measuring equipment becomes longer. When electric characteristics of objects such as semiconductor wafers are to be examined, it is usually preferable that the examination is carried out using a frequency substantially the same as or near to that of signals applied from the objects to be examined. When the cable is long, however, a signal delay of about 1 nsec is caused per 10 cm of the cable. Therefore, the examination cannot be carried out at a high frequency of about 500 MHz. The above-arranged probe apparatus was not satisfactory in this point when it was used to examine such semiconductor chips that must meet high speed for super computers.
Another tester comprising a tester body 2 provided with the measuring equipment and a test head 20 combined with the tester body 2, as shown in FIG. 2, is well-known. In the case of this tester, the cable through which the test head 20 is connected to the measuring equipment is shorter, as compared with the above-mentioned one. This can prevent signal delay from being caused.
However, this tester takes a longer time for measurement because the measuring person must examine a semiconductor chip 22 after it is manually picked up from its packaged cassette and must manually return it to the cassette after the examination is finished. This makes it impossible to examine a large number of matters with high efficiency.